Compare and Research of Spectral Response Characteristic of Transmission-Mode GaAs Photocathode before and after Indium Seal

摘要

Based on the research of the standard second generation, the high capability third generation, the exceeding third generation and the fourth generation, the spectral response of the third generation LLL was carried out using a self-developing spectral response measurement instrument. Spectral response characteristics of third-generation LLL tube were obtained, and the material performance parameters of GaAs photocathode were calculated by curve simulation method. On-line measurement of GaAs photocathode after high-temperature activation and low-temperature activation was carried out, the results showed that spectral response in the whole response waveband decreased after indium seal, and long wave responsibility was most obviously influenced. Decrease was large, cut-off wavelength and peak value wavelength move towards short-wave, peak response value and integral sensitivity decreased, and the final spectral response curve became flat. By calculating photocathode parameters, it was found that indium seal, lead to the variations of surface activation layers of photocathode, and the long wave responded and sensitivity decreased accordingly. The influence factors on the surface activation layers during indium seal were also analyzed.